Blender rendering just one frame when percentage scale is >50% (Cycles)
If the animation works at 50%, you could try doubling the resolution and rendering at 50%.

Maybe the .blend file has some issue.

First you could append the scene to a new file.

If the animation doesn't work yet, you could start from a new file with the default cube and light, and append only camera and path.

Add the other objects until the animation stop at the first frame and check the very last object you've added.